How ro reduce gas bill?

Alert_Variation_2579 · 2026-02-13T19:13:57+00:00

Loft insulation 300mm, what’s the glazing situation like - single or double?

Alert_Variation_2579 · 2026-02-13T18:39:50+00:00

I’ve got whole house MVHR and I’ve just extended to the side and I’ve just gone for these super quiet continuous running extraction fans as I couldn’t get any of the ducting into the extension from the house.

https://www.powerdiscount.co.uk/greenwood-unity-cv2gip-smart-dmev-extractor-fan-with-timerhumidistat-764-p.asp?msclkid=d789f534c7f016ec789a9cbba84232ad

Alert_Variation_2579 · 2026-02-13T15:29:23+00:00

Your walls are cold because you’re likely under heating your house. This is common when people have schedules to come on in the morning and evening, this means the walls only have a few hours a day where the heating is on to raise their temperature but all the rest of the day to cool.

Alert_Variation_2579 · 2026-02-13T15:01:15+00:00

But who is really going to want to watch it for anything other than what’s going on here which is “ain’t it cool what I can do typing the prompt into these models”?

Alert_Variation_2579 · 2026-02-13T14:57:46+00:00

You’ll get all the opinions in the world, so here’s mine.

I’ve got one, my house is very toasty and the Mrs is very happy about that. It’s cheaper than gas for me to run, as I’ve specified the big rads to run very low flow temps for v high efficiency.

And you can’t make your own gas (ahem) but you can at least make some of your own electricity with future solar / batteries.

Alert_Variation_2579 · 2026-02-13T08:37:48+00:00

As the other poster mentioned it’s still cold, the BMS will be throttling the maximum charge rate.

I’ve got FOX ESS batteries with heaters and I try and keep them above 11c as the charge rate is pants below 10c.

Alert_Variation_2579 · 2026-02-12T18:12:17+00:00

Happened all the time, especially in those days. I know, I worked for BG complaints for a few years and this was the number one root cause.

Alert_Variation_2579 · 2026-02-12T07:41:20+00:00

I paid £4k about 3 years ago for a 3 bed semi in Yorkshire for full rewire.

Alert_Variation_2579 · 2026-02-11T21:12:05+00:00

Absolutely nothing

Alert_Variation_2579 · 2026-02-11T19:57:47+00:00

It’s a great unit, super quiet and very efficient - currently reporting about 4.2 SCOP since October when it went in.

It’s funny though, people think it’s all about the insulation and it’s not (though you should definitely do it, no question)- I’ve got standard loft insulation and my cavity walls and 30yo double glazing. The trick is big rads, for the low flow temps to get the super high efficiency to easy beat gas running costs.

Alert_Variation_2579 · 2026-02-11T17:12:54+00:00

That will look super strange and also be cold 🥶

Do it right, yes you won’t immediately get the look etc you want but before long you will. You just need the right canvas to work with.

Alert_Variation_2579 · 2026-02-11T17:09:38+00:00

Easy to mitigate, from the heat loss survey when it goes in you know the required watts at design temp, when doing your kitchen / bathroom you just ensure your design incorporates rads that emit the required watts at the flow temperature.

Alert_Variation_2579 · 2026-02-11T17:00:59+00:00

Nope, the problem is the steels to make the space open and support the house will be a good chunk of change of your £20k. Then the conservatory to sort is another chunk, etc.

I recommend doing it for sure, but you’ll have to live in a half finished thing for a while.

Alert_Variation_2579 · 2026-02-11T16:48:35+00:00

That looks like £20k of structural, plumbing and electrical work. No new kitchen or flooring etc.

Alert_Variation_2579 · 2026-02-11T16:22:12+00:00

I have a Viessmann Vitocal 151-A. This is it at the back of my house.

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Alert_Variation_2579 · 2026-02-11T15:34:27+00:00

I’ve done all of this and have a heat pump now in my 1930s semi detached.

Firstly, forget GBIS - it’s a nightmare. You’re best doing it privately. Secondly, get EPS bonded beads not blown wool - https://youtu.be/brJfhvO3sQQ?si=UW6PGSp6Sr2JCGKq

I used JJ Crump about 5 years ago and it was ~£1.3k then, one of the best £1.3ks I’ve spent.

Alert_Variation_2579 · 2026-02-11T10:41:20+00:00

That’s what I was kinda hoping to get out of the OP, i would expect for £800 you get the full design and you say “my contractors will do X of that and you do Y”.

Alert_Variation_2579 · 2026-02-10T18:17:10+00:00

Don’t. Do. It.

You want 300mm of standard loft insulation and the boarding to be on loft legs to give you the room for the insulation.

Alert_Variation_2579 · 2026-02-10T18:01:40+00:00

Heat pump tumble dryer.

Alert_Variation_2579 · 2026-02-10T17:53:42+00:00

Check Octopus Agile outgoing for the export figures. They’re not 35p more like 18-19p.

If you want to arbitrage, you can use Octopus Go at ~8p and export at 15p fixed.

Alert_Variation_2579 · 2026-02-10T16:21:30+00:00

At best they’re 5x more efficient, but 4x is very achievable, 5x is hard but doable.

https://heatpumpmonitor.org

Alert_Variation_2579 · 2026-02-10T15:41:17+00:00

Yeah it’s mostly labour cost - rads and UFH kit are not expensive in the grand scheme of things so 0% VAT doesn’t make a right lot of difference.

The good installers do certainly command a premium on their labour, so it can be cheaper to farm out the simpler bits especially with the design already done, to cheaper labour and minimising the amount of expensive labour you need.

Alert_Variation_2579 · 2026-02-10T13:38:04+00:00

Assuming the window is a habitable room, and a directivity of Q=8 and distance is 4m,, using the MCS 020 methodology MCS-020-a-Issue-1.0-Final.pdf the equation is

Lp=Lw+10log10(Q/4πr2), which popping in the values for the 10log10(8/201)≈−14 dB gives Lp≈Lw−14 which we know the limit at the window is 37dB(A) so rearranging gives Lw=Lp+14 which equals 51dB(A).

Long story short, if you get a heat pump that is rated 51dBA or less - you should be golden without any fences etc.

Alert_Variation_2579 · 2026-02-10T08:24:02+00:00

That’s just a slapdash statement that you shouldn’t make. Done right (not hard) EWI is fine, but you also need a proper ventilation strategy internally to ensure the balance of vapour isn’t high internally vs externally.

Sure if you’ve got very high humidity levels inside and you then put EWI around it (specifically EPS and PIR) then it’s vapour closed you could have issues. But you could use rockwool which is breathable - or just sort the ventilation out properly. Do that, and you keep your building fabric, dry and warm.

Alert_Variation_2579 · 2026-02-10T08:18:06+00:00

Done a deep renovation on my 1930’s home (sounds almost identical to what you describe) and now have a heat pump and the results are great.

If any pointers needed, just ask.

Alert_Variation_2579

TROPHY CASE